The developmental biology and biomedical communities have had a long-standing interest in understanding how cells with identical genomes establish and maintain remarkably different behaviors and gene expression patterns. Attempts to define specific factors that are sufficient for reprogramming one cell type into another have identified single, or limited combinations of, transcription factors. For example, introduction of the ES cell- expressed transcription factors Oct4/Sox2/Klf4/c-Myc are sufficient to reprogram fibroblasts to a pluripotent state. Ectopic expression of transcription factors is likely to be a general and practical method for reprogramming between arbitrary cellular states. However, we also know from our preliminary studies that the factors themselves are unable to induce the full conversion and we find a great deal of heterogeneity and variability once the pluripotent state is established. Here we aim to dramatically advance our general understanding of reprogramming and pluripotency itself. To accomplish this we will first take advantage of the directionality of the reprogramming process and determine the cell context dependent remodeling capacity (aim 1), and then generate multidimensional data that describe the pluripotent population (aim 2), and finally built tools that enable us to further characterize subpopulations present within pluripotent cell cultures (aim 3). The proposed study presents an opportunity to dramatically alter and accelerate the utility of cellular reprogramming for basic, translational and clinical applications. RELEVANCE (See instructions): The proposed research effort aims to provide a detailed mechanistic understanding of the key protein factors that influence the cell state transitions (somatic to pluripotent) as well as the subsequent maintenance of the pluripotent state. A better understanding of the establishment and maintenance of pluripotency could transform biomedical research and health care delivery.